eg:I am trying to import xyz ETL from other devloper,he has 2 extra column in his target table(eg:A table) with repsect to my targt table A.

So because of the above error ,i added those extra columns(wich other developer has),I am trying to import again ,
It is giving same proble warning like above.
I am viewered ,I ahev all the columns in my model folder wich oother developer has for particular target table.

You need to have an understanding how ODi objects work.
Each column that is being referenced in the mapping has an internal ODI ID. You can see this ID by going to Version tab for any object.
So, when you import the mapping from another developer, that mapping contains the reference to those columns via those IDs.

When you add those columns yourself, they get a new ID. So, even though the column names are the same, the IDs are different. Since ODI remembers them via IDs, you continue to have warnings of missing references.